CVE-2026-84380

5.6 MEDIUM 0.2% exploit odds Fix listed Other

What it is

HTTPX2 is a next generation HTTP client for Python. Prior to 2.11.0, Request._prepare() in src/httpx2/httpx2/_models.py can add a body-derived Content-Length header to a request that already contains a caller-supplied Transfer-Encoding header because its setdefault() processing checks each default header independently rather than treating the two framing headers as mutually exclusive. Fixed-size byte, JSON, form, and known-length multipart bodies can therefore be serialized over HTTP/1.1 with both headers, allowing request smuggling or connection desynchronization when downstream intermediaries disagree about which framing header takes precedence. This issue is fixed in version 2.11.0.

At a glance

Exploitability: Can be exploited over the network without logging in. Limited direct impact.
Exploit odds: 0.2% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-09-02 18:21 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-09-09 21:05 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.2% in the next 30 days (EPSS).
Severity: 5.6 MEDIUM (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2026-09-02 18:21 UTC
Last modified: 2026-09-09 21:05 UTC
Exploit probability: 0.2% · EPSS, next 30 days
Weakness: CWE-444
Record status: Awaiting Analysis

Attack profile CVSS 3.1 · 5.6

Attack vector: Network
Complexity: High
Privileges needed: None
User interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: Low
Availability: Low

Raw vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-84380.md and follow it. Check whether this project is affected by CVE-2026-84380. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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Fix and advisories

References

NVD record · CVE.org record